Plywood structure



May 9, 1944. F. M. wElR ET A1.

PLYWOOD STRUCTURE Filed April 9, 1942 2 SheetSfShee. .l

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PLYWOOD STRUCTURE Filed April 9, 1942 2 Sheets-Sheet 2 FRANC/s M M75/R PA UL Mof. A /V -ATTORNEY Patented May 9, 1944 PLYWOOD STRUCTURE Francis M. Weir and Paul M. Dolan,

- Essex. Conn.

Application April 9, 1942,`Serial No. 438,226

(Cl. 20k-91)l Our invention relates to plywood structures and 1 2 Claims.

has particular reference to structures formed as a combination of corrugated and flat sheets;v

The main object of our invention is to,r provide a structure which will be relatively thick and resistant to deflection, being at the same time" light and inexpensive. We accomplish this pur'- pose by forming .arelatively thick plate of thin sheets of plywood; permanently cementing a corrugated or zig-zag'shaped sheet of a similar material between the.A sheets. In order to simplify the manufacture-'and to obtain a strong junction.

between the-inner.zig-zagiiller and the outer sheets, we' lform theffillerwith the edges so formed that theyA become parallel when the filler is bent into aZig-Zag'shape. A cpnvenient method of obtaining this'result consists in forming triangular grooves alternately at the opposite sides of the sheet, the angle of the grooves being so selected that the edges of the sheet'become parallel at the opposite sides when the sheet is bent into a zig-zag shaped element.

In a modified structure we provide the edges of the zig-zag shaped element with bars or slats having flat sides for cementing them to the outer sheets.

Another object of.' our invention is to provide means to render the structure sound-proof and to improve its heat insulating properties, for which purpose the structure is provided with a coating of a sound-proofing and heat-insulating material.

While our method is particularly suitable for forming hollow structures of plywood sheets, it is understood, of course, that it can be also used with sheets made of other materials such as cardboard, liber, veneer, plastic composition, etc.

Our invention is more fully described in the accompanying specification and drawings, in which:

Fig. 1 is a fractional perspective view of my structure;

Fig. 2 is an edge view of an inner sheet undercut for bending it into a zig-zag shaped member to form an inner filler of the structure;

Fig. 3 is a view of the inner filler folded and ready to be cemented at the edges for building the structure;

Fig. 4 is a perspective view of the filler menibeFig. 5 is a sectional view of a modified structure;

Fig. 6 is a sectional view of. al structure treated for rendering it sound-proof;

Fig. '1 is a sectional view of a modified struc @urti adetail view of an inner member in the-:processcf assembling;

' ig. -9 is a perspective view of a unit member; and

Fig. 1o is s detail view ofrthe modified structurecoated on the inside. f

Our structure as shown in Fig. 1 consists of outer-sheets l and? preferably made of plywood or similar light andjstrong material. Although metal sheets can be used in our structure, we prefer tol use fibrous or plastic non-metallic materials;v Good results areobtained when the outer sheets are made of plywood prepared according to the method as disclosed in the United States patent application Serial No. 376.586, `led January 30, 1941, using veneer sheets I. lf and 2, -2'l with layers of a thermoplastic material 3 therebetween.

The sheets are spaced apart by cementing them to the edges of zig-zag portions 4 of a filler member, or slats, which may be also made of plywood, veneer or similar materials. The filler` sheet is prepared, as shown in Fig. 2, by providing it; with grooves 5, preferably of a triangular shape, and bending the sheet along the lines B opposite the grooves 5. The grooves may be formed by undercutting the material with a suitable tool or by moulding or pressing if the material is suiable for such an operation.

The sheet is folded as shown in Fig. 3 for applying cement 8 to its edges, as by dipping them in a container with a liquid cementitious substance, and then again expanded into' a final shape as shown. in Fig. 4. The sides of the grooves iorm flat surfaces l (Fig. 4) extending in parallel planes when the portions 4 are expanded into a zig-zag shaped or corrugated member.

in order to obtain the at surfaces l for cementing the side sheets l and the angie 9 between one side of the slot and the vertical must be approximately equal to the angle l0 between the portions 4 and the sides l or 2.

A modied structure is shown in Fig. 5, the edges of the slats ll being enclosed in channelshaped bars l2 and secured thereto by a suitable cement 8. The bars l2 help to keep the ller structure in a correct shape before it is cemented to the inner and outer sheeets i and 2 and, moreover, the relatively large outer sides of the bars l2 provide a stronger bond with the outer sheets. 'I'he added bars I2 are especially useful when relatively thin sheets ll are used or when the structure is assembled of individual slats.

Our structure can be conveniently used for making walls and partitions in building and other structures where light weight and low cost are important. Our structure has an added advantage in that it has good heat-insulating properties because of its sealed air cells I3. Another advantage of our structure is that it possesses great strength for its weight and tends to retain its shape under heavy transverse and lateral loads.

Our structure is also particularly suitable for making walls of large air ducts for air-conditioning installations, replacing metal ducts. Our ducts in such installations materially conserve fuel by providing a very good heat insulation. They also have an important advantage in that they absorb or suppress the noise produced by fans and other air-conditioning machinery, unlike metal ducts which readily carry lthese noises to other parts of the building.

The noise-suppressing and insulatingv properties of our structure can'fbe materially increased by providing a coating ofja 'light fluffyi porous, soundfa'bsorbing materiah We have found that good results are obtained by coating the sheets in the structure withl crushed asbestos, exploded mica, rock wool and similar materials l, as shown in Fig. 6. "Tructure for this purpose is dipped into a. solution of aI suitable cementitious materialv such as Iliquid glass, solution of rosin or similar resinous material in a suitable solvent, etc., and, before the cementitious material becomesv dry, dipping the structure into a container with agranulanlumpy or -iiuffy insu latingmaterial it. The same result can be also obtained by spreading orfiiowing the insulating material over the cement-coated structure.

A modified structure is Ishown in Figs. 'l to l0 inclusive. It consists of beams I5 formed by folding a strip of a sheet material, such as veneer, fiber, etc.,l into a rectangular block with a reinforcing diagonal portion' i5 inside, the struc- `ture being therefore -of a zig-zag shape. The

material may be undercut on one side, as shown in Fig. 8, in order to facilitate the bending operation. The beam is reinforced at the corners by angle pieces I1 cemented to the sides of the beam. The assembled member is shown in detail in Fig. 9. A plurality of such beams are placed side by side, the angle pieces I1 being cemented together. Sheets I8, which may be made of plywood or similar material, are then cemented to the angles l1, the complete structure representing a hollow slab of great strength. It can be used for making walls in buildings, refrigerator cars or trucks, airplanes, etc. The structure can be sprayed inside with a suitable cementitious compound, such as sodium silicate, and covered with crushed insulating material I4.

It is understood that my plywood structure may be further modified without departing from the spirit of the invention, as set forth in the appended claims.

We claim as our invention:

1. A method of making a hollow corrugated structure consisting 1n providing opposite sides of a sheet material with alternate parallel grooves, folding the sheet along the lines opposite the grooves so as to open the grooves into substantially flat portions, and attaching outer sheets to the fiat portions so as to obtain triangular prismatic clearances between the folded portions of the inner member and the outer sheets.

2. A hollow corrugated structure comprising a zig-zag shaped inner member formed of a single strip of nonemetallic material undercut at alternating sides and bent at the undercut points to form corners, the outer portions of the corners being thereby formed iiat, the inner angles between the portions being sharp; and outer sheets attached to the iiattened portions of the inner member in parallel relation to each other.

PAUL M. DOLAN. FRANCIS M. WEIR. 

